Waterborne polyurethane bendiocarb microcapsule and preparation method thereof

Abstract

The invention belongs to the technical field of insecticides, and particularly discloses a waterborne polyurethane bendiocarb microcapsule and a preparation method thereof. The waterborne polyurethane bendiocarb microcapsule comprises a capsule wall and a capsule core, the ingredient of the capsule wall is waterborne polyurethane, and the ingredient of the capsule core is a mixture containing bendiocarb; the waterborne polyurethane is prepared from the following raw materials: diisocyanate, polyhydric alcohol and a chain extender, and the mixture is prepared from the following raw materials: bendiocarb powder and an organic solvent for dissolving bendiocarb. According to the preparation method, the bendiocarb microcapsule with the waterborne polyurethane as the wall material is prepared through an interfacial polymerization method, the particle size is small, distribution is uniform, the encapsulation efficiency is high, effective components can be slowly released, and the long-acting mosquito killing effect is achieved. The microcapsule has better stability, is suitable for preparing a water-based environment-friendly spray type insecticide and a water-based environment-friendly insecticidal finishing agent so as to further prepare a long-acting mosquito-repellent textile, and has a good market prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of insecticides, and particularly relates to water-based polyurethane benzylcarb microcapsules prepared by an interfacial polymerization method and a preparation method thereof. Background Art

[0002] A microcapsule is a micron-sized structure that encapsulates one or more substances (called a core material) in an outer shell material (called a wall material), forming a granular structure with a particle size typically ranging from 1 to 1000 microns. The core function of a microcapsule is to protect the core material and control its release, allowing the encapsulated substance to be released under specific conditions or stored for a long time. The components of a microcapsule include a core material and a wall material. The core material is the encapsulated active substance and can be a liquid, solid, or gas. Microcapsules have diverse functions. Depending on the core material, microcapsules can give products properties such as sustained release, long-lasting effect, and targeted delivery. Microcapsules have many advantages, such as protecting the core material, sustained and targeted release, improving operability, reducing side effects or loss, etc. In medicines and cosmetics, microcapsules can reduce the impact on non-target areas and improve effectiveness. Microcapsules are also multifunctional and can give products multiple functions such as antioxidants, antibacterials, fragrance enhancement, and insecticides.

[0003] At the World Health Organization's Third World Anti-Malaria Conference, it was clearly stated that the widespread use of chemical drugs has led to significant insecticide resistance and variability in mosquitoes, and the effectiveness of existing anti-mosquito drugs has gradually diminished. Mefenoxam is one of the public health insecticides recommended by the World Health Organization. It is effective against a variety of pests, including flies, cockroaches, and mosquitoes, with rapid knockdown and long-lasting residual effects. However, Mefenoxam has low solubility in water, and currently, it is primarily used in powders and wettable powders. Powders and wettable powders are prone to drift and loss during use, creating dust pollution, resulting in waste and environmental pollution, and significantly impacting the health of production and operating personnel. These formulations do not meet the requirements for highly effective, low-toxic, safe, and environmentally friendly mosquito repellents. Furthermore, the Mefenoxam component in powders and wettable powders is exposed to air and easily oxidized, making it less durable and limiting its application in mosquito repellent technology. Microencapsulation technology encapsulates the active ingredient of bendiocarb within a capsule wall material, which protects the pesticide and provides controlled release. By mixing bendiocarb microcapsules with a solution containing water, a surfactant, and a thickener, a bendiocarb microcapsule suspension is prepared. This aligns with the development trend of highly effective, low-toxic, safe, and environmentally friendly water-based pesticide formulations.

[0004] CN 105284841 A and CN 105696329 A both disclose a bendiocarb microcapsule and a preparation method. The bendiocarb microcapsule walls produced in these two patents are both polyurea, which is typically synthesized by reacting isocyanates (such as TDI and IPDI) with amine compounds (such as DETA and triethylenetetramine). This reaction is very rapid and difficult to control, and the stability of the emulsion needs to be maintained for a short period of time, which may lead to uneven formation or rupture of the microcapsules. The solvent for bendiocarb is a relatively toxic organic solvent such as dichloromethane or acetone. These organic solvents are highly volatile during the reaction, and bendiocarb may precipitate, preventing complete encapsulation. Furthermore, the patents only contain scanning electron micrographs, not transmission electron micrographs, which cannot fully demonstrate the presence of the bendiocarb core in the microcapsule to prove successful encapsulation. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a water-based polyurethane benzylcarb microcapsule and a preparation method thereof, which effectively improves the uniformity of the particle size distribution and the embedding rate of the water-based polyurethane benzylcarb microcapsule and the stability of the reaction.

[0006] In order to achieve the above object, the specific technical solutions adopted by the present invention are as follows:

[0007] In a first aspect, the present invention provides a method for preparing aqueous polyurethane fenvalerate microcapsules, comprising the following steps:

[0008] a) preparing the oil phase: dissolving the technical drug of bendiocarb in an organic solvent and stirring magnetically until completely dissolved, then adding the diisocyanate to form an oil phase, and finally adding the catalyst, and stirring magnetically at room temperature of 25°C for 1 to 1.5 hours;

[0009] b) preparing an aqueous phase: dispersing an emulsifier and a dispersant in water, adding a polyol, and stirring at room temperature (25° C.) for 1 to 1.5 hours to form an aqueous phase;

[0010] c) preparing an emulsion: adding the oil phase from step a) to the water phase from step b) and stirring at a constant speed and temperature of 48° C. to form an oil-in-water emulsion;

[0011] d) Microencapsulation: adding the chain extender dropwise to the emulsion of step c), and continuing to stir at a constant temperature of 48° C. for 2 h to form a uniform aqueous polyurethane benzylcarb microcapsule emulsion;

[0012] e) Post-treatment: After centrifugation, washing and drying, the aqueous polyurethane benzylcarb microcapsules are obtained.

[0013] Furthermore, the weight ratio of the diisocyanate, polyol and chain extender is 1:(0.9-1.08):(0.16-0.2); the content of the catalyst is 1.3%-1.5% by weight of the diisocyanate; the diisocyanate is an aromatic or aliphatic diisocyanate, the polyol is a polyether polyol or a polyester polyol, the chain extender is 1,4-butanediol (BDO), and the catalyst is one or more of dibutyltin dilaurate (DBTDL), stannous octoate, and dibutyltin diacetate.

[0014] Furthermore, the diisocyanate is selected from one or more of 2,4-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate;

[0015] The polyol is selected from one or more of polyethylene glycol, polypropylene glycol, polyethylene adipate glycol, polybutylene adipate glycol, polycaprolactone diol, polycarbonate diol, polylactic acid, polybutylene succinate, and polytetramethylene ether glycol.

[0016] Furthermore, in step a), the organic solvent is a mixture of one or more of ethyl acetate, butyl acetate, isobutyrate, ethyl propionate, ethyl butyrate, ethyl hexanoate, ethyl lactate, and phenylacetate, and the mass ratio of the organic solvent to benomyl is (3-6):1.

[0017] Furthermore, in step b), the emulsifier is a mixture of one or more of sodium dodecyl sulfonate, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, Tween, Span, poloxamer, OP-10, gum arabic, gelatin, and styrene-maleic anhydride copolymer, and the emulsifier content is 1% to 5% of the total mass of the capsule wall and capsule core; the dispersant is selected from polyvinyl alcohol 1788 or 1799, and the dispersant content is 21% to 24% of the total mass of the capsule wall and capsule core.

[0018] Furthermore, in step c), the stirring rate is 400-600 rpm, preferably 500 rpm; and in step e), the centrifugal speed is 8000-13000 rpm.

[0019] In a second aspect, the present invention provides aqueous polyurethane bendiocarb microcapsules produced using the above-described preparation method. These microcapsules comprise a capsule wall composed of aqueous polyurethane and a capsule core composed of a mixture containing bendiocarb. The aqueous polyurethane is made from diisocyanate, polyether polyol or polyester polyol, and a chain extender, while the mixture comprises bendiocarb powder (99% by mass) and an organic solvent for dissolving the bendiocarb.

[0020] Furthermore, the particle size of the microcapsule is 0.8 to 5 μm, preferably 0.8 to 2 μm; the embedding degree is 84% ​​to 96%, preferably 96%.

[0021] Furthermore, the core-to-wall ratio of the microcapsule is controlled within the range of (5:1) to (1:5), preferably 2:1.

[0022] Furthermore, the solid content of the microcapsules is 6% to 10%, preferably 8%.

[0023] The present invention has the following beneficial effects:

[0024] 1. The present invention provides water-based polyurethane bendiocarb microcapsules and a method for preparing the same. The prepared water-based polyurethane bendiocarb microcapsules have a smaller microcapsule particle size, a more uniform particle size distribution, and a higher encapsulation efficiency (particle size of 0.8 to 5 μm, and an encapsulation efficiency of 84% to 96%). Firstly, the smaller microcapsules provide a larger specific surface area, which helps increase the coverage area of ​​the bendiocarb technical. The microsizing of the microcapsules helps increase the probability of mosquitoes contacting the insecticide, thereby improving the utilization rate of the bendiocarb technical while reducing its environmental pollution. Furthermore, the more uniform particle size distribution also helps improve the utilization rate of the bendiocarb technical.

[0025] 2. The present invention utilizes interfacial polymerization to prepare polyurethane microcapsules. This overall preparation method offers the advantages of short reaction time, simple operation, mild conditions, and strong operability. The reactive monomers of the polyurethane microcapsules of the present invention are isocyanate compounds, which have the advantages of high functionality, fast reaction rate, low toxicity, and mild reaction conditions. During the preparation of the polyurethane microcapsules, the present invention improves the overall performance of the polyurethane microcapsules containing benzylpyridinium chloride by modifying the types and amounts of additives such as emulsifiers, dispersants, and chain extenders, as well as adjusting the core-shell ratio.

[0026] 3. The present invention uses an ester solvent, which is more environmentally friendly and allows for easy control of the waterborne polyurethane preparation process. Scanning electron microscopy, transmission electron microscopy, and liquid chromatography tests were performed on the microcapsules, demonstrating the effective preparation of waterborne polyurethane microcapsules containing benzimidazole using various indicators. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a flow chart for the preparation of water-based polyurethane benzylcarb microcapsules of the present invention.

[0028] Figure 2 The scanning electron micrograph of the aqueous polyurethane benzylcarb microcapsules obtained in the examples is shown in FIG. In the figure, 1:2, 1; 1, 2:1, and 3:1 correspond to samples in Examples 1, 2, 3, and 4, respectively.

[0029] Figure 31 is a particle size distribution diagram of the aqueous polyurethane benzylcarb microcapsules obtained in the examples.

[0030] Figure 4 TEM image of the aqueous polyurethane benomyl microcapsules obtained in the example.

[0031] Figure 5 This is a liquid phase test chart of the free benomyl core content of each sample in the examples.

[0032] Figure 6 This is a liquid phase test chart of the total core content of the sample diflubenzuron in the example. DETAILED DESCRIPTION

[0033] The present invention is further described below with reference to the accompanying drawings and specific examples. The experimental methods used in the following examples are conventional methods unless otherwise specified; the materials, reagents, etc. used in the following examples are all commercially available unless otherwise specified.

[0034] Example 1

[0035] A water-based polyurethane benzylcarb microcapsule, the preparation process is as follows Figure 1 As shown, the specific preparation method is as follows:

[0036] a) Prepare the oil phase: Dissolve 2.34 g of the technical drug bendiocarb in 13 g of ethyl acetate and stir magnetically at an appropriate speed. Once completely dissolved, add 2.23 g of isophorone diisocyanate to form an oil phase. Finally, add 0.03 g of dibutyltin dilaurate and stir magnetically at room temperature (25°C) for 1-1.5 hours.

[0037] b) Preparing an aqueous phase: Disperse 0.18 g of sodium lauryl sulfate and 1.62 g of 1788 polyvinyl alcohol in 79 g of water, then add 2 g of PEG400 to form an aqueous phase. Stir and mix at room temperature (25° C.) for 1 to 1.5 hours to form an aqueous phase.

[0038] c) preparing an emulsion: adding the oil phase from step a) to the water phase from step b) and stirring at a constant speed (500 rpm) at a constant temperature of 48° C. to form an oil-in-water emulsion;

[0039] d) Microencapsulation: 0.45 g of BDO was added dropwise to the emulsion from step c), and the mixture was stirred at a constant temperature of 48° C. for 2 h to form a uniform aqueous polyurethane emulsion of benomyl microcapsules;

[0040] e) Post-treatment: After centrifugation at 10,000 rpm, washing and drying, the aqueous polyurethane benzylcarb microcapsules are obtained.

[0041] Example 2

[0042] A water-based polyurethane fenvalerate microcapsule, the specific preparation method is as follows:

[0043] a) Preparation of the oil phase: Dissolve 4.68 g of the bendiocarb raw material in 24 g of ethyl acetate and stir magnetically at an appropriate speed. After complete dissolution, add 2.23 g of isophorone diisocyanate to form an oil phase. Finally, add 0.03 g of dibutyltin dilaurate and stir magnetically at room temperature (25°C) for 1-1.5 hours.

[0044] b) Preparing an aqueous phase: Disperse 0.24 g of sodium lauryl sulfate and 2.15 g of 1788 polyvinyl alcohol in 105 g of water, then add 2 g of PEG400 to form an aqueous phase. Stir and mix at room temperature (25° C.) for 1 to 1.5 hours to form an aqueous phase.

[0045] c) preparing an emulsion: adding the oil phase from step a) to the water phase from step b) and stirring at a constant speed (500 rpm) at a constant temperature of 48° C. to form an oil-in-water emulsion;

[0046] d) Microencapsulation: 0.45 g of BDO was added dropwise to the emulsion from step c), and the mixture was stirred at a constant temperature of 48° C. for 2 h to form a uniform aqueous polyurethane emulsion of benomyl microcapsules;

[0047] e) Post-treatment: After centrifugation at 10,000 rpm, washing and drying, the aqueous polyurethane benzylcarb microcapsules are obtained.

[0048] Example 3

[0049] A water-based polyurethane fenvalerate microcapsule, the specific preparation method is as follows:

[0050] a) Preparation of the oil phase: 9.36 g of the bendiocarb raw material was dissolved in 47 g of ethyl acetate and magnetically stirred at an appropriate speed. After complete dissolution, 2.23 g of isophorone diisocyanate was added to form an oil phase. Finally, 0.03 g of dibutyltin dilaurate was added and magnetically stirred at room temperature (25°C) for 1-1.5 hours.

[0051] b) Preparing an aqueous phase: Disperse 0.28 g of sodium lauryl sulfate and 3.2 g of 1788 polyvinyl alcohol in 158 g of water, then add 2 g of PEG400 to form an aqueous phase. Stir and mix at room temperature (25° C.) for 1 to 1.5 hours to form an aqueous phase.

[0052] c) preparing an emulsion: adding the oil phase from step a) to the water phase from step b) and stirring at a constant speed (500 rpm) at a constant temperature of 48° C. to form an oil-in-water emulsion;

[0053] d) Microencapsulation: 0.45 g of BDO was added dropwise to the emulsion from step c), and the mixture was stirred at a constant temperature of 48° C. for 2 h to form a uniform aqueous polyurethane emulsion of benomyl microcapsules;

[0054] e) Post-treatment: After centrifugation at 10,000 rpm, washing and drying, the aqueous polyurethane benzylcarb microcapsules are obtained.

[0055] Example 4

[0056] A water-based polyurethane fenvalerate microcapsule, the specific preparation method is as follows:

[0057] a) Preparation of the oil phase: 14.04 g of the bendiocarb raw material was dissolved in 70 g of ethyl acetate and magnetically stirred at an appropriate speed. After complete dissolution, 2.23 g of isophorone diisocyanate was added to form an oil phase. Finally, 0.03 g of dibutyltin dilaurate was added and magnetically stirred at room temperature (25°C) for 1 to 1.5 hours.

[0058] b) Preparing an aqueous phase: Disperse 0.48 g of sodium lauryl sulfate and 4.3 g of 1788 polyvinyl alcohol in 210 g of water, then add 2 g of PEG400 to form an aqueous phase. Stir and mix at room temperature (25° C.) for 1 to 1.5 hours to form an aqueous phase.

[0059] c) preparing an emulsion: adding the oil phase from step a) to the water phase from step b) and stirring at a constant speed (500 rpm) at a constant temperature of 48° C. to form an oil-in-water emulsion;

[0060] d) Microencapsulation: 0.45 g of BDO was added dropwise to the emulsion from step c), and the mixture was stirred at a constant temperature of 48° C. for 2 h to form a uniform aqueous polyurethane emulsion of benomyl microcapsules;

[0061] e) Post-treatment: After centrifugation at 10,000 rpm, washing and drying, the aqueous polyurethane benzylcarb microcapsules are obtained.

[0062] The following characterization tests were performed on the water-based polyurethane benzylcarb microcapsules prepared in the examples.

[0063] 1. Dimensions

[0064] The microcapsules were tested by scanning electron microscopy and transmission electron microscopy. Figure 2 The results of scanning electron microscopy are shown in Figure 2. Figure 3 The results of the capsule particle size show that the capsule particle size is small and the distribution is relatively uniform. Figure 4 Transmission electron microscopy results show that benomyl was successfully encapsulated in water-based polyurethane.

[0065] 2. Determination of Encapsulation Efficiency

[0066] 1. Sample Pretreatment

[0067] (1) Determination of free cores: The microcapsule suspension was centrifuged at high speed (12,000 rpm, 10 minutes) to precipitate the microcapsules and retain the free cores in the supernatant. The supernatant was then directly measured for the free core concentration (C1) by liquid chromatography.

[0068] (2) Total core determination: Take an equal amount of microcapsule suspension and disrupt the microcapsules to release the encapsulated cores. Disruption methods include: adding a solvent to dissolve the polyurethane shell (e.g., DMSO, THF, acetone), vortexing or sonicating (30 minutes). Centrifuge (12,000 rpm, 10 minutes) to remove shell fragments. The supernatant is then collected and the total core concentration (C2) is determined by liquid chromatography.

[0069] 2. Liquid chromatography conditions

[0070] Chromatographic column: Select according to the properties of the core substance (such as C18 reverse phase column).

[0071] Mobile phase: Optimize gradient or isocratic elution conditions to ensure good separation of free core and solvent / impurity peaks.

[0072] 3. Calculation of embedding rate

[0073]

[0074] 4. Results of embedding efficiency determination

[0075] The results of liquid phase tests on microcapsules are as follows Figures 4-5 As shown, the free core content and the total content of benomyl in the sample are respectively shown. The liquid phase test data are summarized in the following Table 1.

[0076] Table 1

[0077]

[0078] The embedding rate results calculated based on the data in Table 1 are shown in Table 2 below. The embedding rate of the microcapsules in Examples 1 to 4 is between 84% and 96%, indicating a high embedding degree.

[0079] Table 2

[0080] sample Core-to-wall ratio Embedding rate (%) Particle size (um) Example 1 1:2 91 0.86 Example 2 1:1 95 1.79 Example 3 2:1 96 1.6 Example 4 3:1 84 2.41

[0081] This specific implementation is merely an explanation of the present invention and is not a limitation of the present invention. Any changes made by those skilled in the art after reading the specification of the present invention will be protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A method for preparing water-based polyurethane fenvalerate microcapsules, characterized in that: The following steps are involved: a) preparing the oil phase: dissolving the technical drug of bendiocarb in an organic solvent and stirring magnetically until completely dissolved, then adding the diisocyanate to form an oil phase, and finally adding the catalyst, and stirring magnetically at room temperature of 25°C for 1 to 1.5 hours; b) preparing an aqueous phase: dispersing an emulsifier and a dispersant in water, adding a polyol, and stirring at room temperature (25° C.) for 1 to 1.5 hours to form an aqueous phase; c) preparing an emulsion: adding the oil phase from step a) to the water phase from step b) and stirring at a constant speed and temperature of 48° C. to form an oil-in-water emulsion; d) Microencapsulation: adding the chain extender dropwise to the emulsion of step c), and continuing to stir at a constant temperature of 48° C. for 2 h to form a uniform aqueous polyurethane benzylcarb microcapsule emulsion; e) Post-treatment: After centrifugation, washing and drying, the aqueous polyurethane benzylcarb microcapsules are obtained.

2. The method for preparing aqueous polyurethane benzylcarb microcapsules according to claim 1, characterized in that: The weight ratio of the diisocyanate, the polyol and the chain extender is 1:(0.9-1.08):(0.16-0.2); the content of the catalyst is 1.3%-1.5% by weight of the diisocyanate; the diisocyanate is an aromatic or aliphatic diisocyanate, the polyol is a polyether polyol or a polyester polyol, the chain extender is 1,4-butanediol, and the catalyst is one or more of dibutyltin dilaurate, stannous octoate, and dibutyltin diacetate.

3. The method for preparing aqueous polyurethane benzylcarb microcapsules according to claim 2, characterized in that: The diisocyanate is selected from one or more of 2,4-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate; The polyol is selected from one or more of polyethylene glycol, polypropylene glycol, polyethylene adipate glycol, polybutylene adipate glycol, polycaprolactone diol, polycarbonate diol, polylactic acid, polybutylene succinate, and polytetramethylene ether glycol.

4. The method for preparing water-based polyurethane benzylcarb microcapsules according to claim 1, characterized in that: In step a), the organic solvent is a mixture of one or more of ethyl acetate, butyl acetate, isobutyrate, ethyl propionate, ethyl butyrate, ethyl hexanoate, ethyl lactate, and phenylacetate, and the mass ratio of the organic solvent to benomyl is (3-6):

1.

5. The method for preparing water-based polyurethane benzylcarb microcapsules according to claim 1, characterized in that: In step b), the emulsifier is a mixture of one or more of sodium dodecyl sulfonate, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, Tween, Span, poloxamer, OP-10, gum arabic, gelatin, and styrene-maleic anhydride copolymer, and the content of the emulsifier is 1% to 5% of the total mass of the capsule wall and the capsule core; the dispersant is selected from polyvinyl alcohol 1788 or 1799, and the content of the dispersant is 21% to 24% of the total mass of the capsule wall and the capsule core.

6. The method for preparing water-based polyurethane benzylcarb microcapsules according to claim 1, characterized in that: In step c), the stirring speed is 400-600 rpm; in step e), the centrifugal speed is 8000-13000 rpm.

7. The aqueous polyurethane benzylcarb microcapsules prepared by the preparation method according to any one of claims 1 to 6, characterized in that: The invention comprises a capsule wall and a capsule core, wherein the capsule wall is composed of water-based polyurethane, and the capsule core is composed of a mixture containing bendiocarb; the raw materials of the water-based polyurethane include diisocyanate, polyol and chain extender, and the raw materials of the mixture include bendiocarb powder and an organic solvent for dissolving bendiocarb.

8. The aqueous polyurethane benzylcarb microcapsules according to claim 7, characterized in that: The particle size of the microcapsule is 0.8-5 μm, and the embedding degree is 84%-96%.

9. The aqueous polyurethane benzylcarb microcapsules according to claim 7, characterized in that: The core-to-wall ratio of the microcapsule is controlled within the range of (5:1) to (1:5).

10. The aqueous polyurethane benzylcarb microcapsules according to claim 7, characterized in that: The solid content of the microcapsule is 6% to 10%.

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